1. Field of the Invention
The present invention relates to a lighting device, and more particularly to a lighting device using a field emission type electron emitter.
2. Description of the Prior Arts
There has recently been proposed a thin-sized lighting device wherein electrons are emitted from an electron emission cathode by applying an electric field in a vacuum and the emitted electrons are caused to collide with a phosphor applied on an anode to thereby emit light (see Japanese Unexamined Patent Application No. 2001-15077). In such a lighting device, the anode is configured such that a transparent conductive film (ITO) and a phosphor are formed on a glass substrate.
In the lighting device described above, electrons emitted from the electron emission cathode to be accelerated collide with the phosphor to emit light, thereby giving residual energy to the anode. The anode generates heat by this energy. When high voltage is applied between the anode and the cathode in order to provide a bright light-emission, in particular, the heat generation from the anode becomes remarkably great, thereby bringing a possibility of damaging the lighting device. Further, in case where the light-emission is not uniform, it is necessary to provide a diffusion plate to the anode for diffusing light to obtain uniform light-emission.
The present invention reduces the heat generation from the anode as much as possible and enables a uniform illumination without a diffusion plate.